Does this test have other names?
Carbon dioxide test, CO2 test
What is this test?
This test measures the amount of bicarbonate, a form of carbon dioxide, in your blood.
Bicarbonate, also known as HCO3, is a byproduct of your body's metabolism. Your blood
brings bicarbonate to your lungs, and then it is exhaled as carbon dioxide. Your kidneys
also help regulate bicarbonate. Bicarbonate is excreted and reabsorbed by your kidneys.
This regulates your body's pH, or acid balance. Bicarbonate also works with sodium,
potassium, and chloride, also called electrolytes. These are usually measured at the
same time as bicarbonate.
This test is usually part of a comprehensive series of blood tests to check for certain
Why do I need this test?
You may have the bicarbonate test to monitor issues that affect pH levels in your
blood. You may also have this test if you have kidney disease, liver failure, or other
conditions related to metabolism.
What other tests might I have along with this test?
Your healthcare provider may also order several other tests. These may include:
Arterial blood gas analysis
Electrolyte (sodium, potassium, and chloride) testing
Urine pH testing
Anion gap blood testing
What do my test results mean?
Many things may affect your lab test results. These include the method each lab uses
to do the test. Even if your test results are different from the normal value, you
may not have a problem. To learn what the results mean for you, talk with your healthcare
Results are given in milliequivalents per liter (mEq/L) or millimoles per L (mmol/L).
Normal bicarbonate levels are:
A high level of bicarbonate in your blood can be from metabolic alkalosis, a condition
that causes a pH increase in tissue. Metabolic alkalosis can happen from a loss of
acid from your body, such as through vomiting and dehydration. It may also be related
to conditions including anorexia and chronic obstructive pulmonary disease (COPD).
A low level of bicarbonate in your blood may cause a condition called metabolic acidosis,
or too much acid in the body. A wide range of conditions, including diarrhea, kidney
disease, and liver failure, can cause metabolic acidosis.
How is this test done?
The test requires a blood sample, which is drawn through a needle from a vein in your
Does this test pose any risks?
Taking a blood sample with a needle carries risks that include bleeding, infection,
bruising, or feeling dizzy. When the needle pricks your arm, you may feel a slight
stinging sensation or pain. Afterward, the site may be slightly sore.
What might affect my test results?
Eating acidic fruits could affect your results. Medicines that may raise your levels
Medicines that may lower your levels include:
How do I get ready for this test?
You don't need to prepare for this test. But be sure your healthcare provider knows
about all medicines, herbs, vitamins, and supplements you are taking. This includes
medicines that don't need a prescription and any illicit drugs you may use.